1. Field of the Invention
The invention relates to abrasive flow machining and, more particularly, the use of abrasive flow machining to polish the region of intersection between a branch outlet and a passageway in a body.
2. Background Art
Abrasive flow machining is used for working metals and related materials, particularly for machining and finishing internal shapes, bores, orifices and complex three-dimensional shapes and as an alternative to certain other difficult machining operations. Abrasive flow machining is particularly used for deburring, radiusing, resizing, and polishing/finishing operations.
Abrasive flow machining incorporates the use of a plastic or semi-solid media containing abrasive particles distributed substantially uniformly throughout. The purpose of the semi-solid media is to transport the abrasive particles through a passage of a workpiece to achieve the desired machining results as illustrated in U.S. Pat. No. 5,054,247, which is hereby incorporated by reference.
Abrasive flow machining may incorporate the use not only of a plastic or semi-solid media containing abrasive particles, but may additionally include a liquid or oil-based media also containing abrasive particles distributed substantially uniformly throughout. A liquid media will provide easier cleanup through passageways and medium delivery tubes.
Nevertheless, whether the abrasive media is a semi-solid media, a liquid, or oil-based media, ideally, the media may range in look and feel from a highly viscous material to an extremely low viscosity fluid. The most effective media for a specific application will depend upon the geometric characteristics of the application and the materials to be abraded or polished.
The application-specific media would have such viscosity and rheology that it flows at a suitable rate through an outlet or orifice under an imposed or gravitational force where the rate is defined by the abrasive flow processing requirements.
Considerations for media selection for a particular application may be based upon a number of considerations. Preferably, the media must flow through a delivery tube and through passageways requiring surface, radius, or opening machining by the abrasive flow process. Furthermore, the media must exhibit sufficient Theological behavior during flow through passageways to achieve the desired machining action. Additionally, the media must maintain coherence during flow sufficient to achieve the radiusing action where and when it is required. Finally, the media must provide a machining action and lubrication to such a degree to maintain the required flow rates and perform the appropriate abrasive processing.
Suitable types of media that possess the desired rheological behaviors required for this application include those identified in U.S. Pat. No. 5,679,058, entitled xe2x80x9cAbrasive Jet Cutting Mediumxe2x80x9d, assigned to the assignee of the present invention and herein incorporated by reference. Also appropriate for this application is media that contains a supraparticle structure or a sufficiently flexible and shearable, yet sufficiently cohesive microstructure.
When the workpiece consists of a body having a passageway with multiple openings extending over the length of the passageway, such as, for example, a fuel rail or automobile manifold, the abrasive flow machining in the region of the intersection of the multiple branch outlets with the passageway of the body is accomplished by flowing the abrasive media through the passageway to each branch outlet. For purposes of discussion, a body having a passageway will encompass a manifold, pipe, tube, or conduit with at least one inlet and two or more outlets.
Directing attention to FIG. 1, a sectioned schematic is illustrated of a body 10 having a passageway 11 including multiple branch outlets 15 each defined by an opening 20 extending through a wall 25 of the body 10. A typical branch outlet 15 having an opening 20 will be discussed with the understanding that such a discussion may also be applied to any of the remaining branch outlets and associated openings. The opening 20 of a branch outlet 15 is typically created by a drilling operation which leaves, as illustrated in FIG. 2, a burr 30 around the periphery 35 of the opening 20. The burr 30 protrudes from the opening 20 and creates a discontinuity on the body inner surface 40 at the intersection region 37 defined by the intersection of the periphery 35 of the opening 20 with the body wall 25.
FIG. 1 illustrates a prior art technique for removal of burrs 30 and subsequent polishing of the underlying surface by abrasive flow machining. In particular, a flowable abrasive media 45 is introduced into a passageway 11 from one end 55 of the passageway 11. The media 45 is moved under pressure toward opposite end 60 of the passageway 11. The burr 30 is removed and the underlying surface polished by the flow of the abrasive media 45 over the surface of the burr 30. For a body 10 having multiple branch outlets, as illustrated in FIG. 1, it is necessary to direct the flow of the media 45 through at least one branch outlet 15 at a time.
It should be appreciated the abrasive flow technique is most effective with ample media flow through any one branch outlet 15 and, therefore, while it may be possible to pass the media 45 through a number of different branch outlets, it is oftentimes preferred to direct the media 45 through a single branch outlet 15 to maximize the effectiveness of the abrasion technique.
To accomplish this, the body 10 is mounted within an assembly having a plurality of plugs which may be selectively activated to seal one or more branch outlets 15 thereby preventing flow of the media 45 through that branch outlet 15. For purposes of discussion, a single plug 65 will be addressed with the understanding that this plug is representative of the remaining plugs. As illustrated in FIG. 1, when the plug 65 is moved away from the branch outlet 15, the media 45 flows past the opening 20 and is ejected at the branch outlet 15.
Using this technique, the burr 30, illustrated in FIG. 2, is largely removed from the periphery 35 of the opening 20 as illustrated in FIG. 3.
While this technique is effective in removing a large portion of the burr 30, as illustrated in FIG. 3, there is still a portion of the burr 30 remaining. This is created by the unidirectional flow of the media 45 in the passageway 11 and results not only in a small burr 30 remaining but, furthermore, results in a non-uniform radiusing of the periphery 35 of the opening 20. In particular, the abrasion of an upstream surface 70 on the periphery 35 of the opening exceeds that of a downstream surface 75, as illustrated in FIG. 3.
Additionally, the assembly used for manipulating the plurality of plugs, which act to block media 45 flow through the branch outlets, is a fairly complex assembly and must be customized for each body. Such an arrangement is very costly and setup using such an arrangement is time-consuming. Furthermore, physical interference caused by the assembly makes it difficult to capture and contain the media 45 as it leaves the branch outlet 15. Finally, using the arrangement illustrated in FIG. 1, the entire passageway 11 is filled with abrasive media 45 and then the media 45 is selectively released through the desired outlet 15 to initiate the abrasion process. This creates a surplus of media 45 within the passageway 11 that must be removed when the abrasion process is complete.
A method is needed for directing the flowable abrasive media 45 through the passageway 11 in an efficient manner without the need of the complex assembly utilizing movable plugs, without requiring the associated extensive setup time, and without the need to completely fill the passageway with media prior to the abrasion process.
Furthermore, a method is desired to eliminate the non-uniform abrasion about the periphery 35 of the opening 20 caused by the unidirectional flow of the flowable abrasive media 45.
In a first embodiment of the invention, for a body having a wall with an inner surface along a passageway and at least one branch outlet defined by an opening extending through the wall, a method for abrading the inner surface at an intersection region defined by the intersection of the periphery of the opening at the wall comprises the steps:
a) positioning a first media delivery tube within a first end of the passageway, wherein the first tube has an inlet and an outlet and wherein the outlet is proximate to the periphery of the opening;
b) supplying a flowable abrasive media through the inlet of the first tube to the outlet; and
c) guiding the media from the outlet of the first tube through the opening.
Guiding the media may involve positioning a deflector within the passageway to direct the flow of media through the opening.
In a second embodiment of the invention, a second media delivery tube may be positioned within the passageway opposite the first media delivery tube and media provided through it such that the opposing flow of media from the first and second tubes is directed through the opening.
In a third embodiment of the invention, the first and second media delivery tubes are combined into a single tube having a tube outlet between two inlets. The tube outlet is aligned with the opening in the passageway and media is directed through the opening.
In a fourth embodiment, baffles are attached to the first delivery tube around the tube outlet, thereby defining a flow path from the tube outlet directly through the opening.
Both methods and assemblies are associated with each of these embodiments.